Field of the Invention
The present invention relates to a method, system and computer program for determining the orientation of an apparatus attached to a vehicle.
Description of the Related Technology
It is known to provide tracking devices for installation in or on vehicles. The tracking device can include a positioning system, such as a satellite positioning system such as a Global Positioning System (GPS) receiver or the like, and a transmitter for reporting data to a control center. In addition to the GPS or other receiver, the vehicle may also have an accelerometer. In some cases, the accelerometer may be a component of the tracking device.
Data from an accelerometer can be used for various purposes, for example to provide information on driving style or to detect when a vehicle is in a collision. However, the accelerometer axes are very unlikely to be aligned with the axes of the vehicle. For example, to simplify installation an accelerometer, or a tracking device including an accelerometer, can be installed in a variety of positions and orientations with respect to a vehicle with little or no regard to the orientation of the accelerometer relative to the vehicle.
It would be desirable for the accelerometer data to be expressed in terms of the vehicle frame of reference, rather than the accelerometer axes (which relate to the orientation of the accelerometer).
US2009/051510A1 relates to a system and method for detecting and reporting vehicle damage. A monitoring unit can include an accelerometer module with a tri-axial accelerometer. A self-orienting application is started after installation to determine the mounting position of the unit and how to compensate for it. First a gravity vector is determined by observing the forces on the accelerometers due to gravity when the vehicle is stopped. US2009/051510A1 then assumes that when a vehicle begins to move or is braking the vehicle is usually traveling in a straight line along the center line of the vehicle. By measuring acceleration or braking, a center line orientation can be determined.